Reduction Of Aryl Alkyl Ketones Research Articles

ChemInform Abstract: Asymmetric Reduction of Ketones by Phosphoric Acid Derived Catalysts.

AbstractCatalytic systems involving a BINOL‐derived phosphoric acid are developed for the enantioselective reduction of aryl alkyl ketones with catecholborane.

Cyclometalated Complexes of Ruthenium, Rhodium and Iridium as Catalysts for Transfer Hydrogenation of Ketones and Imines

AbstractA library of organometallic compounds derived from primary and secondary amines cyclometalated by ruthenium(II), rhodium(III) and iridi‐ um(III) was tested in the asymmetric transfer hydrogenation of a number of ketones and imines. All compounds displayed high catalytic activity for the reduction of ketones under mild conditions. The most enantioselective catalysts were based on secondary amines containing two asymmetric carbon atoms bound to the nitrogen atom. For the reduction of aryl alkyl ketones [Ar(CO)R where R=CH3 or CH2R′] the cyclometalated ruthenium and rhodium derivatives of the (2R,5R)‐2,5‐diphenylpyrrolidine ligand displayed the best results with respect to activity and selectivity (ees up to 97%). However, for the reduction of aryl tert‐alkyl ketones [Ar(CO)R′′ in which R′′ is a tertiary alkyl group] the best catalyst was a ruthenium compound derived from bis[(R)‐1‐phenylethyl]amine, allowing the reduction of isobutyrophenone and cyclohexyl phenyl ketone which were both reduced with high enantioselectivities (ees up to 98%). This shows that the cyclometalated compounds have a high substrate specificity. In addition, acyclic and cyclic imines were reduced with good selectivities by both rhodium(III) and iridium(III) metalacycles built up with (2R,5R)‐2,5‐diphenylpyrrolidine.

ChemInform Abstract: Ruthenium‐Catalyzed Asymmetric Transfer Hydrogenation of Ketones in Ethanol.

A ruthenium catalyst formed in situ by combining [Ru(p-cymene)Cl2]2 and an amino acid hydroxy-amide was found to catalyze efficiently the asymmetric reduction of aryl alkyl ketones under transfer hydrogenation conditions using ethanol as the hydrogen donor. The secondary alcohol products were obtained in moderate to good yields and with good to excellent enantioselectivity (up to 97% ee).

Ruthenium-catalyzed asymmetric transfer hydrogenation of ketones in ethanol

A ruthenium catalyst formed in situ by combining [Ru( p-cymene)Cl 2] 2 and an amino acid hydroxy-amide was found to catalyze efficiently the asymmetric reduction of aryl alkyl ketones under transfer hydrogenation conditions using ethanol as the hydrogen donor. The secondary alcohol products were obtained in moderate to good yields and with good to excellent enantioselectivity (up to 97% ee).

Rhodium-catalyzed asymmetric transfer hydrogenation of alkyl and aryl ketones in aqueous media

A novel lipophilic rhodium catalyst was evaluated in the enantioselective transfer hydrogenation of ketones in water using sodium formate as the hydride donor, and in the presence of sodium docecylsulfonate. Alkyl alkyl ketones were reduced in good yields and in moderate to good enantioselectivities, and the reduction of aryl alkyl ketones proceeded with excellent enantioselectivity (up to 97% ee).

Highly enantioselective ruthenium-catalyzed reduction of ketones employing readily available Peptide ligands.

Highly efficient and selective catalysts for the asymmetric reduction of aryl alkyl ketones under hydrogen-transfer conditions (2-propanol) were obtained by combining a novel class of pseudo-dipeptide ligands with [[RuCl(2)(p-cymene)](2)]. A library of 36 dipeptide-like ligands was prepared from N-Boc-protected alpha-amino acids and the enantiomers of 2-amino-1-phenylethanol and 1-amino-2-propanol. The catalyst library was evaluated with the reduction of acetophenone and excellent enantioselectivity of 1-phenylethanol was obtained with several of the novel catalysts. A ligand based on the combination of N-Boc-L-alanine and (S)-1-amino-2-propanol (ligand A-(S)-4) was found to be particular effective. When the situ formed ruthenium complex of this ligand was employed as the catalyst in the hydrogen-transfer reaction of various aryl alkyl ketones, the corresponding alcohol products were achieved in excellent enantioselectivity (up to 98 % ee).

Pinacol Reduction‐cum‐Rearrangement. A Re‐examination of the Reduction of Aryl Alkyl Ketones by Zinc—Aluminum Chloride.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Pinacol reduction-cum-rearrangement. A re-examination of the reduction of aryl alkyl ketones by zinc–aluminum chloride

Reduction of alkyl phenyl ketones by zinc and aluminum chloride in acetonitrile results in pinacol condensation followed by rearrangement. The phenyl group migrates in every instance.

Aminosulf(ox)ides as ligands for Iridium(I)-catalyzed asymmetric transfer hydrogenation

A new class of efficient catalysts was developed for the asymmetric transfer hydrogenation of unsymmetrical ketones. A series of chiral N,S-chelates (6-22) was synthesized to serve as ligands in the iridium(I)-catalyzed reduction of ketones. Both formic acid and 2-propanol proved to be suitable as hydrogen donors. Sulfoxidation of an (R)-cysteine-based aminosulfide provided a diastereomeric ligand family containing a chiral sulfur atom. The two chiral centers of these ligands showed a clear effect of chiral cooperativity. In addition, aminosulfides containing two asymmetric carbon atoms in the backbone were synthesized. Both the sulfoxide-containing beta-amino alcohols and the aminosulfides derived from 1,2-disubstituted amino alcohols gave rise to high reaction rates and moderate to excellent enantioselectivities in the reduction of various ketones. The enantioselective outcome of the reaction was favorably affected by selecting the most appropriate hydrogen donor. Enantioselectivities of up to 97% were reached in the reduction of aryl-alkyl ketones.

ChemInform Abstract: Suitably Designed Chiral Amino Alcohols: Synthesis, Resolution and Application to the Catalytic Enantioselective Reduction of Aryl Alkyl Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Suitably designed chiral amino alcohols: synthesis, resolution and application to the catalytic enantioselective reduction of aryl alkyl ketones

The amino alcohol rac-1-(1,2,3,4-tetrahydroisoquinoline-1-yl)-cyclopentanol was resolved via its O,O′-dibenzoyl-tartaric acid salt. These enantiomeric amino alcohols were used in the enantioselective reduction of prochiral aryl alkyl ketones. The resulting secondary alcohols were obtained in high enantiomeric excess.

Asymmetric Reduction. Part III1 Reduction of Aryl Alkyl Ketones with Chiral Alkoxyaluminodichlorides and Studies on the Nature of the Transition States

Asymmetric Reduction. Part III1 Reduction of Aryl Alkyl Ketones with Chiral Alkoxyaluminodichlorides and Studies on the Nature of the Transition States